1. Field of the Invention
The present invention relates to a method and apparatus for light deflecting, and more particularly to a method and apparatus for light deflecting capable of efficiently moving a floating mirror with an electrostatic attraction force.
2. Discussion of the Background
Conventionally, a light deflecting device and a light deflecting system using the light deflecting device are known, generating an electrostatic attraction force to bend a cantilever-like light reflecting member to change a reflection direction relative to input light rays. This apparatus is described in Japanese Patent No. 2,941,952, Japanese Patent No. 3,016871, Japanese Laid-Open Patent Application Publication No. 10-510374, “Applied Physics Letters,” 1977, vol. 31, No. 8, pp 521–pp 523, by K. E. Petersen, and “Optics Letters,” vol. 7, No. 9, pp 688–pp 690 by D. M. Bloom.
Further, an image forming apparatus is also known, employing a light deflecting system in which a plurality of digital micro-mirror devices are arranged in one or two dimensions. This apparatus is described in Japanese Laid-Open Patent Application Publication No. 06-138403.
In digital micro-mirror devices having a twisted-type light reflection member or a cantilever-like light reflecting member, a mirror-portion is tilted and has at least one fixed end. This device is described in a reference of “Proc. SPIE,” 1989, vol. 1150, pp 86–pp 102.
However, in the light deflecting device and the digital micro-mirror device having the twisted-type light reflecting member or the cantilever-like light reflecting member, the light reflecting member is difficult to be stably held and a response speed is late.
Also, in the above-mentioned digital micro-mirror device having the twisted-type light reflecting member, a hinge of the twisted portion may degrade its mechanical strength in a usage over an extended period of time.
Further, a light deflecting device for switching light by driving a diffraction grating with an electrostatic attraction force limits an allowable wavelength of an input light ray.
In addition, Japanese Laid-Open Patent Application Publication No. 2000-002842 describes a light deflecting device for performing a light deflection by causing a light reflecting member with both ends fixed to deform in a circular shape. This device requires a relatively high driving voltage since the light reflecting member is fixed at both ends.
Further, Japanese Laid-Open Patent Application Publication No. 08-220455 describes a mirror movable in two-axis directions and a display apparatus using this mirror. In this mirror and apparatus, a mirror plate made of a magnetic metal in a pan-like shape is fixed with a needle pivot by a magnetic force to a mirror bed including a magnet, and a plurality of electrodes are formed on the mirror bed. When the electrodes are applied with different voltages, a voltage difference is generated between the electrodes and the mirror plate by the action of electrostatic and the mirror plate is moved about the top of the needle pivot to come close to the electrodes. In this case, however, the mirror plate is substantially fixed to the mirror base at the needle pivot with the magnetic force. This structure is relatively complex and the mirror plate is actually not held in a completely free condition.
Due to this structure, in which the mirror plate is made of a magnetic metal, the magnet is arranged under the mirror bed, and magnetic yokes are arranged around the mirror bed, it is very difficult to make the two-axis movable mirror and the apparatus using the mirror through a micromachining process. In addition, the two-axis movable mirror and the apparatus using the mirror may emit magnetic force and the environments for these apparatuses may be limited.